3-Heterothio{8 (alkoxycarbonyl)thioacetyl{9 cephalosporanic derivatives

ABSTRACT

R is lower alkyl, phenyl, or phenyl-lower alkyl; R4 is a fiveor six-membered nitrogen and/or sulfur or oxygen-containing ring system; are useful as antibacterial agents.   wherein R1 is hydrogen, lower alkyl, phenyl or certain heterocyclic groups; R2 is lower alkyl or phenyl-lower alkyl; R3 is hydrogen, lower alkyl, phenyl-lower alkyl, tri(lower alkyl)silyl, tri(lower alkyl)stannyl, a salt forming ion, or   3-Heterothio((alkoxycarbonyl)thioacetyl)cephalosporin derivatives which have the formula

United States Patent [191 Treuner et al.

[ Dec. 16, 1975 HETEROTHIO[ (ALKOXYCARBONYL )THI- OACETYL]CEPHALOSPORANIC DERIVATIVES [75] Inventors: Uwe D. Treuner; Hermann Breuer,

both of Regensburg, Germany [73] Assignee: E. R. Squibb & Sons, Inc.,

Princeton, NJ.

[22] Filed: Aug. 30, 1974 [21] Appl. No.: 501,905

[52] US. CL... 260/243 C; 260/294.8 E; 260/329 S; 260/347.2; 260/455 R; 424/246 Sassiver et al., Antimicrobial Agents & Chemeotherapy, l968, pp. lO1-lO8, (1969).

Lewis et al., Antimicrobial Agents & Chemeotherapy, 1968, pp. 1091l4, (1969).

Primary Examiner-Nicholas S. Rizzo Assistant Examiner-Diana G. Rivers Attorney, Agent, or Firm-Lawrence S. Levinson; Merle J. Smith [57] ABSTRACT 3-I-leter0thio[(alkoxycarbonyl)thioacetyl]cephalosporin derivatives which have the formula CH S--R COOR wherein R is hydrogen, lower alkyl, phenyl or certain heterocyclic groups; R is lower alkyl or phenyl-lower alkyl", R; is hydrogen, lower alkyl, phenyl-lower alkyl, tri(lower alkyl)silyl, tri(lower alkyl)stannyl, a salt forming ion, or

R is lower alkyl, phenyl, or phenyl-lower alkyl; R, is a fiveor six-membered nitrogen and/0r sulfur or oxygen-containing ring system; are useful as antibacterial agents.

10 Claims, No Drawings 3-I-IETEROTHIO[ ALKOXYCARBONYL )THI- OACETYL1CEPHALOSPORANIC DERIVATIVES SUMMARY OF THE INVENTION This invention relates to a new 3-heterothio [(alkoxycarbonyl)thioacetyl]cephalosporin derivatives which have the formula especially hydrogen, pivaloyloxymethyl, sodium or potassium. R is lower alkyl;

R, is thiadiazole, tetrazole and their methyl substituted analogs, especially, 1,3,4-thiadiazole, 5-methyl- R is hydrogen, lower alkyl, phenyl, thienyl, furyl or pyridyl.

R is lower alkyl or phenyl-lower alkyl.

R, is hydrogen, lower alkyl, tri(lower alkyl)silyl, tri(- lower alkyl)stannyl, phenyl-lower alkyl, a salt forming ion, or

DETAILED DESCRIPTION OF THE INVENTION The various groups represented by the symbols have the meanings defined below and these definitions are retained throughout this specification.

The lower alkyl groups are straight or branched chain hydrocarbon groups containing 1 to 8 carbon atoms, preferably 1 to 4 carbons. Examples of the type of these groups are methyl, ethyl, propyl, isopropyl, butyl, tbutyl, pentyl, isopentyl, etc. The phenyl-lower alkyl groups include such lower alkyl groups attached to a phenyl, e.g., benzyl, phenethyl, benzhydryl, etc.

The salt forming ions represented by R are metal ions, e.g., alkali metal ions such as sodium or potassium, alkaline earth metal ions such as calcium or magnesium, or an amine salt ion, of which a number are known for this purpose, for example, lower alkylamines like methylamine or triethylamine, aralkylamines like dibenzylamine, N,N-dibenzylethylenediamine, N-ethylpiperidine, etc.

Preferred embodiments of this invention are as follows:

R is hydrogen, lower alkyl of l to 4 carbons, phenyl, benzyl, furyl, thienyl or pyridyl, especially hydrogen and phenyl;

R is lower alkyl of l to 4 carbons, especially methy or ethyl;

R is hydrogen, alkali metal, trimethylsilyl or 1,3,4-thiadiazole, tetrazole and l-methyltetrazole.

The new derivatives of [(alkoxycarbonyl)thioacetyl]cephalosporins of this invention are produced by reacting 7-aminocephalosporanic acid (7-ACA) (or derivative wherein R is other than hydrogen) with a mercaptan HSR at a pH of about 8 8.5 to obtain the derivative of the formula COOR The product of formula II is then acylated on the amino group with an oxycarbonylthioacetic acid of the formula or an activated derivative of the former (II).

The activated derivatives referred to include, for example, the acid chloride or reaction product with an anhydride forming reagent such as ethylchloroformate, benzoyl chloride, pivaloyl chloride, etc., or with bisimidazolecarbonyl, dicyclohexylcarbodiimide, pnitrophenol or the like.

According to a preferred modification, the 7- aminocephalosporanic acid derivative of formula II, in an organic solvent like tetrahydrofuran is added to a mixture containing the acid of formula III and dicyclohexylcarbodiimide in an organic solvent like the one mentioned above at a reduced temperature of about 0C. The dicyclohexylurea formed during the reaction is removed and the product is recovered from the filtrate.

According to another modification, reaction between the 7-aminocephalosporanic acid compound of formula [I and the oxycarbonylthioacetic acid is effected, for example, by converting the latter to the acid chloride with an agent such as thionyl chloride and adding, at a low temperature, e.g., C. or below, the acid chloride to a mixture of the 7-aminocephalosporanic acid and a salt forming organic base, such as triethylamine, pyridine or the like, in an inert organic solvent such as chloroform, methylene chloride, dioxane, benzene or the like. The product of the reaction is then isolated by conventional procedures, e.g., by concentration or evaporation of the solvent.

Alternatively, 7-ACA or a derivative thereof (R in formula II is other than hydrogen), can be first acylated as described in our copending application Ser. No. 468,715, filed May 10, 1974, then the product of this reaction is made to react with the mercaptan PIS-R at an alkaline pH, e.g., about pH 7.8.

The acids of formula III are formed by reacting a mercaptoacetic acid of the formula with a chlorofonnic acid ester of the formula (V) 0 ll in the presence of an inorganic or organic base, e.g., an alkali metal hydroxide such as potassium hydroxide or triethylamine or dimethylaniline.

When R is the acyloxymethyl group Cl-l- OCO-R, this group can be introduced onto the 7-ACA moiety prior to the reaction with the acid of formula III by treatment with one to two moles of a halomethyl ester of the formula (VI) mun-1 0C012 wherein hal is halogen, preferably chlorine or bromine, in an inert organic solvent such as dimethylformamide, acetone, dioxane, benzene or the like at about ambient temperature or below.

Further process details are also provided in the illustrative examples.

Certain of the compounds of this invention may exist in difierent optically active forms. The various stereoisomeric forms as well as racemic mixtures are within the scope of the invention.

The compounds of this invention have antibacterial activity against both gram positive and gram negative organisms such as Staphylococcus aureus, Proteus retrgeri and E. lzafniae. They may be used as antibacterial agents in a prophylactic manner or to combat infections caused by organisms such as those named above, and in general can be utilized in a manner similar to cephradine and other cephalosporins. For example, a compound of formula I or a physiologically acceptable salt thereof can be used in various animal species in an amount of about 1 to 100 mg./kg. daily, orally or parenterally, in single or two to four divided doses to treat infections of bacterial origin, e.g., 4.0 mg./kg. in mice.

Up to about 600 mg. of a compound of formula I or a physiologically acceptable salt thereof can be incorporated in an oral dosage form such as tablets, capsules or elixirs or in an injectable form in a sterile aqueous EXAMPLE 1 DL-2[ [(Ethoxycarbonyl )thio]phenyl ]acetic acid 3.4 gms. (20 mM) of a-mercaptophenylacetic acid are dissolved with 2.2 gms. (40 mM) of potassium hydroxide in 50 ml. of water. 25 ml. of chloroform are i added and, at a temperature of 5, 2.2 gms. (25 mM) of ethyl chloroformate are added dropwise with intensive stirring. After 14 hours, the chloroform phase is separated, the water phase is acidified with 2N hydrochloric acid and extracted with ether. After drying and evaporating the solvent, 2.6 gms. of white crystalline DL-2- [[(ethoxycarbonyl)thio]phenyl]acetic acid are obtained, m.p. l08l 10.

EXAMPLE 2 DL-2-[ (Methoxycarbonyl )thio]phenyl ]acetic acid By substituting methyl chloroformate for the ethyl chloroformate in the procedure of Example 1, white crystalline DL-2-[ methoxycarbonyl )thio ]phenylacetic acid is obtained, m.p. 58.

EXAMPLE 3 DL-2-[( Methoxycarbonyl )thio]-2-phenylacetic acid chloride 2.8 gms. mM) of the acid obtained in Example 2 are heated with 15 ml. of thionyl chloride and 15 ml. of absolute ether for 24 hours under reflux with the exclusion of water vapor. After evaporating the solvent and excess thionyl chloride, crude DL-2-[(methoxycarbonyl)thio]-2-phenylacetic acid chloride is obtained which is used in the next step without further purification.

EXAMPLE 4 7-[ [DL-2-[(Methoxycarbonyl )thio]-2-phenylacetyl- ]amino] -3-( hydroxymethyl )-8-oxo-5-thial -azabicyclo[4.2.0]oct-2-ene-carboxylic acid, 3-acetate A solution of 1.9 gms. (10 mM) of the product of Example 3 in a little chloroform is added dropwise at a temperature of to a solution of 2.7 gms. 10 mM) of 7-ACA and 2 gms. of triethylamine in chloroform, with'stirring. The mixture is stirred for 20 minutes at 20 and 18 hours at room temperature. The solution cools to 0, ml. of 2N hydrochloric acid are added and the solution shaken well. The chloroform is separated and washed twice each with ml. of water. It is then dried over sodium sulfate and after evaporating the solvent, the 7-[[DL-2-[(methoxycarbonyl)thio]-2- phenylac etyl amino -3- hydroxymethyl )-8-oxo-5-thial-azabicyclo[4.2.0]oct-2-ene-carboxylic acid, 3-acetate is obtained in the form of a sticky mass which, after the addition of chloroform, solidifies. After recrystallization from methylene chloride/carbon tetrachloride, the pure product forms as light beige crystals, m.p. 74-75 (dec.).

The potassium salt is obtained by the freeze drying of a solution containing one equivalent each of the acid and potassium bicarbonate, m.p. 175 (dec.).

EXAMPLE 5 7-[ [DL-2- Ethoxycarbonyl )thio]-Z-phenylacetyl- ]amino]-3-( hydroxymethyl )-8-oxo-5-thial-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid, 3-acetate By substituting DL-2-[[(ethoxycarbonyl)thio]- phenyllacetic acid for the DL-2-[ [(methoxycarbonyl)- thio]pheny1]acetic acid in the procedure of Example 3 and then following the procedure of Example 4 with the product, 7-[ [DL-2-[(eth0xycarbony1)thio]-2- phenylacetyl amino -3-( hydroxymethyl )-8-oxo-5-thial-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid, 3-acetate is obtained m.p. 1 12.

The potassium salt is obtained by the procedure of Example 4, mp. 167.

The following additional products are similarly obtained:

7-[ [DL-2- ethoxycarbonyl )thio]acetyl]amino]-3- (hydroxymethyl )-8-oxo-5-thia- 1 -azabicyclo 4. 2. oct- 2-ene carboxylic acid 3-acetate 7-[ [DL-2- n-butoxycarbonyl )thio]acetyl]amino]-3- (hydroxymethyl )-8-oxo-5-thial -azabicyclo[4.2.0]oct- 2-ene carboxylic acid-3-acetate 7-[ DL-2- benzyloxycarbonyl )thio]-2- phenylacetyl amino -3-( hydroxymethyl -8-oxo-5-thia- 1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid-3-acetate 7-[ [DL-2- Benzyloxycarbonyl )thio acetyl amino 3-(hydroxymethyl)-8-oxo-5-thial-azabicyc1o[4.2.- 0loct-2-ene-2-carboxylic acid-3-acetate.

EXAMPLE 6 3-[[(5-Methyl-1,3 ,4-thiadiazol-2-yl )thio]methyl]-7- amino-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2- carboxylic acid A mixture of 13.6 g. (0.5 M) of 7-aminocepha1osporanic acid (7-ACA) in 100 m1. of water and 50 m1. of acetone are brought to pH 8 with sodium hydroxide while stirring. 9.8 g. (0.57 M) of 2-methyl-l,3,4- thiadiazole-S-thiol are added and the mixture is heated at 80 for 4 hours. After cooling to this is acidified to pH 3.5 with dilute hydrochloric acid and stirred for minutes. The precipitated solid is filtered under suction and washed with acetone. This 3-[[(5-methyl- 1,3,4-thiadiazo1-2-yl )thio] methyl]-7-amino-8-oxo-5- thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid is purified by dissolving in sodium bicarbonate solution and reprecipitating with 2N hydrochloric acid; yield 12.7 g., m.p. 206.

EXAMPLE 7 3-[[(3-Methyl-1,2,4-thiadiazol-5-yl)thio]methyl]-7- amino-S-oxo-S-thia- 1 -azabicyclo[ 4.2.0]oct-2-ene-2-carboxylic acid By substituting 3-methyl-1,2,4-thiadiazo1e-5-thiol for the 2-methy1-1,3,4-thiadiazole-5-thiol in the procedure of Example 6, 11.6 g. of 3-[[(3-methyl-1,2,4- thiadiazol-S-yl )thio]methyl]-7-amino-8-oxo-5-thial azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid. mp. 186 (dec.) are obtained.

EXAMPLE 8 3-[ l-Methyl- 1 H-tetrazol-S-yl )thio]methyl ]-7-amino- 8-oxo-5-thia-1-azabicyc1o[4.2.0]oct-2-ene-2-carboxylic acid By substituting 0.57 M of l-methyl-1H-tetrazol-5- thiol for the 2-methyl-1,3,4-thiadiazol-5-thiol in the procedure of Example 7, 3-[[( l-methyl-ll-l-tetrazol-S- yl )thio] methyl]-7-amino-8-oxo-5-thia- 1 -azabicyc1o[4.2.0]oct-2-ene-2-carboxylic acid is obtained.

EXAMPLE 9 3-[ [(5-methyl-1 ,3,4-thiadiazo1-2-yl )thio]methyl ]-7- amino-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2- carboxylic acid, diphenylmethyl ester 18 g. of 7-amino-3-[[(5-methyl-l,3,4-thiadiaz01-5- yl)thio]methyl]-8-oxo-5-thia-1-azabicyclo[4.2.0]oct- 2-ene-2carboxylic acid are suspended in 350 ml. of tetrahydrofuran. 4.1 ml. of perchloric acid are added dropwise. After 30 minutes, a slightly turbid solution forms. This solution is filtered and to the filtrate is added dropwise with stirring 12 g. of diphenyldiazomethane and 20 ml. of tetrahydrofuran. After 3 hours, the reaction mixture is poured into 2 liters of absolute ether. The solid, light brown precipitate, which is the perchloric acid salt of the desired product, is dried over Kieselgel in a dessiccator. To obtain the base, the perchloric acid salt is dissolved in water and treated with the calculated equivalent of potassium bicarbonate. The aqueous solution obtained is extracted with chloroform. The chloroform phase is treated with activated carbon and sodium sulfate to obtain the 10 g. of the product, 7-amino-3-[[(5-methyl- 1 ,3,4-thiadiazo1-2-yl )thio]methyl]-8 -oxo-5-thia-1- azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid, diphenylmethyl ester, as a light brown powder, m.p. l57159. The product is recrystallized from tetrahydrofuran/petroleum ether. The isomeric thiadiazolyl derivative is similarly obtained from the product of Example 7.

EXAMPLE i0 3-[ l-Methyll H-tetrazol-S-yl )thio]methyl1-7-amino- 8-oxo-5-thial -azabicyclo[4.2.0]oct-2-ene-carboxylic acid, diphenylmethyl ester The product, 7-amino-3- l-methyl-1H-tetrazol-5- yl )thio]methyl1-8-oxo-5 -thia-1-azabicyc1o[4.2.0]0ct- 2-ene-carboxylic acid, diphenylmethyl ester, m.p. 168l69 (dec.), is obtained by the procedure of Example 9 utilizing as starting material 7-amino-3-[[( lmethyl-1l-l-tetrazol-S-yl)thio]methyl]-8-oxo-5-thia-1- azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid.

EXAMPLE 1 1 3-[ l -Methyl-1l-l-tetrazol-S-yl)thio]methyl]78- [[[(methoxycarbonyl )thio]phenylacetyl]amino]-8- oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid diphenylmethyl ester 1.1. g. (5 mM) of the product of Example 2 is dissolved in 25 ml. of tetrahydrofuran and added at 0 to 1.0 g. of dicyclohexylcarbodiimide in 5 ml. of tetrahydrofuran. After 30 minutes, 2.48 gm. of 3-[[( l-methy1- 1l-l-tetrazol-S-yl)thio]methyll-7-amino-8-oxo-5-thia-1- azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid diphenylmethyl ester dissolved in 15 ml. of tetrahydrofuran is added. After stirring for 12 hours, the dicyclohexylurea which has formed isfiltered off. The filtrate is treated with activated carbon and the solvent is drawn off leaving 3-[ l-methyl-1H-tetrazol-5-yl)thio]methyl]-7B-[ methoxycarbonyl )thio]phenylacetyl- ]amino]-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2- carboxylic acid diphenylmethyl ester as a light brown powder, yield 2.7 g., m.p. 9294 (dec.).

EXAMPLE l2 3-[ 1-Methy1-1H-tetrazol-S-yl)thio]methy1]-7B- methylcarbonyl )thio phenylacetyl]amino]-8-oxo- -thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid 2 g. of the product of Example 1 1 is stirred in a mixture of ml. of trifluoroacetic acid and 3 ml. of anisole at 0 for 15 minutes. After the solvent is drawn off and the residue is treated with ether/petroleum ether (1:1 the solid brown residue is taken up in sodium bicarbonate solution, filtered and the filtrate is extracted with ethyl acetate and then acidified to pH 2.5 with 2N hydrochloric acid while cooling with ice. This is extracted with ethyl acetate. The organic phase is treated with activated carbon and the solvent is drawn off to obtain the product 3-[[( l-methyl-ll-l-tetrazol-S- yl )thio]methyl ]-'7,8-[ meth'oxycarbonyl )thio]- phenylacetyl amino ]-8-ox o-5-thial -azabicyclo 4.2.- 0]oct-2-ene-2-carboxylic acid. The product is recrystallized from tetrahydrofuran/petroleum ether as a light brown powder, yield 0.5 g., m.p. 128 (dec.).

EXAMPLE 13 3-[ 1 -Methyll H-tetrazol-S-yl )thio methyl]- 7B-[ [[(methoxycarbonyl )thio]phenylacetyl ]amino]-8- oxo-5-thia- 1 -azabicyclo 4 2 .0 oct-2-ene-2-carboxylic acid, potassium salt The potassium salt of the product of Example 12 is obtained by freeze drying an equimolar aqueous solution of the acid of that example and potassium bicarbonate, m.p. l53154 (dec.).

EXAMPLES l4 44 The products below are obtained by reacting the acid 3-[ l-methyll H-tetrazol-S-yl )thio]methyl1-7-ACA 8 3-[[(5-methyl-3-isoxazolyl)thio]methyl]-7-ACA 3-[[( l,2,4-thiadiazol-3-yl)thio]methyl]-7-ACA 3-[[(5-butyl-1,2,4-thiadiazol-3-yl)thio]methyl]-7- ACA 3-[ 3-methy1-4-isoxazolyl )thio methy1]-7-ACA 3-[[(3-methyl- 1 ,2.4-0xadiazol-5-yl )thio]methyl ]-7- ACA 3-[ 5-ethyl-3-isothiazolyl )thio methyl]-7-ACA 3-[[(2-methyl-1,3,4-thiadiazol-5-yl)thio]methy1]-7- ACA 3-[[( 1,2,4-thiadiazol-5-yl )thio]methyl]-7-ACA 3-[ l Z-pyridinyl-N-oxide )thio]methyl ]-7-ACA Example 14: 7,8-[[[[2-(methoxycarbonyflthio]-2-(2-pyridyl- )acetyl]amino]-3-[ l .3,4-thiazol-2-y1)thio]methyl]- 8-oxo-5-thial -azabicycl0[4.2.0]oct-2-ene-2- carboxylic acid 15: 7B-[ [2-(n-butoxy)carbonyl ]thio]- 2(phenylacety1]amino]-3-[ 1.3,4-0xadiazol-2- yl )thio]methyl]-8-oxo-5-thial -azabicyclo[ 4.2.- 0]oct-2-ene-2-carboxy1ic acid 16: 7B-[ [2-ethoxy)carbonyl ]thio]-2-( 2-pyridyl- )acetyl ]amino]-3-[ [(S-ethyl-l ,3.4-oxadiazol-2- yl)thio]methyl]-8-oxo-5-thia-1-azabicyclo[4.2.- 0]oct-2-ene-2-carboxylic acid 17: 7,B-[[[[2-(methoxy)carbonyl]thio]acetyl- ]amino]-3-[ 3-methyl-5-isothiazoly1)thio]methyl]-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2- carboxylic acid oct-7B- [(2-ethoxy )carbonyl]thio ]-2-( Z-thienyl- )acetyl]amino]-3-[ [(3-isothiazolyl )thio]methyl]- 8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid 19: 7/3-[ 2-(benzyloxy)carbonyl ]thio]-2- phenylacetyl]amino ]-3-[ 3-is0xazolyl )thio]methyl]- 8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2- carboxylic acid 20: 7,B-[[[[2-(methoxy)carbony1]thio]-2- phenylacety11amino ]-3-[ 5-methyl-3-isoxazolyl thio] methyl1-8-oxo-5-thial -azabicyclo[4.2.0]oct- 2-ene-2-carboxylic acid 21: 7B-[ [2-(propoxy)carbonyl]thio]-2- phenylacetyl]amino]-3-[ 1,2,4-thiadiazo1-5- y1)thio]methyl]-8-oxo-5-thial-azabicyclo[4.2.- 0]oct-2-ene-2-carboxylic acid 22: 7/3-[[[[2-(phenethoxy)carbonyl]thio]acetyl- ]amino]-3-[[(1,2,4-thiadiazol-3-yl)thio]methyl]- 8-oxo-5-thia-l-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid phenylacetyl]amino ]-3-[ S-butyl-l .2,4- thiadiazol-3-yl )thio methyl]-8-oxo-5-thial azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid 24: 7B-[ [2-( methoxy )carbonyl ]thio]butyramido]- 3-[ l.2,3,4-tetrazol-5-yl)thio]methyl]-8-oxo-5- thia-l -azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid 25: 7,B-[[[(2-benzyloxy)carbonyl]thio]propionamido]3-[ [(5-methyl-3-is0thiazolyl )thio methyl]- 8-oxo-5-thial -azabicyclo[4.2.0 oct-2-ene-2- carboxylic acid 26: 7,8-[ [2-(methoxy)carbonyl]thio]-2- phenylacetyllamino ]-3-[ 3-isoxazolyl )thio]methyl]- 8-oxo-5-thia- 1 -azabicyclo[4.2.0]0ct-2-ene-2- carboxylic acid 27: 7B-[[[[2-(butoxy)carbonyl]thio]-2- phenylacetyUamino]-3-[[(3-methyl-4-isoxazolyl)- 

1. A COMPOUND OF THE FORMULA
 2. A compound as in claim 1 wherein R1 is phenyl.
 3. A compound as in claim 1 wherein R1 is hydrogen.
 4. A compound as in claim 1 wherein R1 is phenyl, R2 is lower alkyl, R3 is hydrogen and R4 is (lower alkyl)tetrazole.
 5. A compound as in claim 4 wherein each lower alkyl group is methyl.
 6. Alkali metal salt of the compound of claim
 5. 7. A salt as in claim 6 wherein the alkali metal is potassium.
 8. A compound as in claim 1 wherein R1 is phenyl, R2 is lower alkyl, R3 is hydrogen and R4 is (lower alkyl)thiadiazole.
 9. A compound as in claim 8 wherein R2 is methyl and R4 is 5-methyl-1,3,4-thiadiazole.
 10. A compound as in claim 1 wherein R1 is hydrogen, lower alkyl of 1 to 4 carbons, phenyl, benzyl, furyl, thienyl or pyridyl; R2 is lower alkyl of 1 to 4 carbons. R3 is hydrogen, alkali metal, trimethylsilyl or 